KUWAIT, Jan 17 (Reuters) - A start-up airline in the United States has offered a 25 percent stake to Qatar Airways, Chief Executive Akbar al-Baker said on Wednesday, giving the Gulf carrier a second chance to buy into a U.S. airline.

Qatar Airways tried to buy up to 10 percent of listed American Airlines last year, but changed its mind in August after opposition from the U.S. carrier's management.

The start-up airline was private and so Qatar Airways would not face the same opposition this time, Baker told reporters at an air show in Kuwait.

However, he declined to name the airline or disclose where it would be based and did not say if Qatar Airways intended to purchase the stake.

Those acquisitions added to a portfolio of airline holdings that includes 20 percent of British Airways-parent International Consolidated Airlines Group, and 10 percent of South America's LATAM Airlines Group SA.

Baker said Qatar Airways' owner, the government of Qatar, is open to swapping up to 49 percent of its shares with other airlines in which the Gulf carrier has stakes.

"We would be the largest carrier of the world," he said of his idea to create a virtual mega-airline.

Qatar Airways was blocked last year from flying to the lucrative markets of Saudi Arabia and the United Arab Emirates because of restrictions imposed by those countries.

Baker said the airline would make a significant loss in the 12 months to March 31 due to those restrictions which also blocks the airline from flying over Saudi Arabia and the UAE.

Baker also expressed regret about management changes at Airbus, including the impending departure of Chief Operating Officer Fabrice Bregier, due to step down in February.

"Airbus is going into uncharted waters," Baker said, warning that other staff could also leave the European planemaker.

Bregier was long assumed to be the heir apparent to Chief Executive Tom Enders, who is to leave the company next year.

"Not having a continuity of management will, I think, be very disruptive to Airbus."

Airbus declined to comment on Baker's remarks. Qatar Airways is one of the largest Middle East airlines and is a major customer of Airbus and its rival, Boeing. (Additional reporting by Tim Hepher in Paris; Writing by Saeed Azhar; Editing by Jane Merriman and Keith Weir)